////////////////////////////////////////////////
// DESCRIPTION:
//     Exclusion Synchronization class
//
// Legal Notices:
//     Copyright (c) 2008, Telliam Consulting, LLC.
//     All rights reserved.
//
//     Redistribution and use in source and binary forms, with or without modification,
//     are permitted provided that the following conditions are met:
//
//     * Redistributions of source code must retain the above copyright notice,
//       this list of conditions and the following disclaimer.
//
//     * Redistributions in binary form must reproduce the above copyright notice,
//       this list of conditions and the following disclaimer in the documentation
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//
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//       may be used to endorse or promote products derived from this software
//       without specific prior written permission.
//
// Disclaimer:
//     THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
//     ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
//     WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
//     IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
//     INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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//     OF THE POSSIBILITY OF SUCH DAMAGE.  
//

#pragma once

namespace FusionWare
{
    namespace Threads
    {
        ///////////////////////////////////////////////////////////////////////////////
        // Description:
        //    Implements an Exclusion locking system based on a critical section
        //
        // Comments:
        //    Implements a locking mechanism that allows
        //    all threads access until one requests exclusive access.
        //    The thread requesting exclusive access waits until all
        //    other threads have released the resource before it is allowed
        //    exclusive access.
        // 
        // Note:
        //    Instances of this class will be accessed by multiple threads. So, 
        //    all members of this class (except the constructor and destructor) 
        //    must be thread-safe.
        //
        class CExclusionLock
        {
        public:
            CExclusionLock();
            ~CExclusionLock();

            void Lock(BOOL Exclusive = FALSE);
            void Unlock(BOOL Exclusive = FALSE);

        protected:
            void ModifyCount(DWORD AddVal,BOOL Exclusive);

        private:
            HANDLE m_hZero;      // Signaled when data value is 0
            DWORD m_Count;       // -1 for exclusive access  >0 for non exclusive count
            CriticalSection m_csCount;
        };

        // attempt to do a non exclusive lock
        inline void CExclusionLock::Lock(BOOL Exclusive /*=FALSE*/)
        {
            ModifyCount(1,Exclusive);
        }

        inline void CExclusionLock::Unlock(BOOL Exclusive /*=FALSE*/)
        {
            ModifyCount(-1,Exclusive);
        }


        // Auto Lock to handle special case of exclusion requests
        template<class LockType,BOOL Exclusive>
        class TAutoLockEx
        {
            public:
            TAutoLockEx(LockType& rlt) : m_Lock(rlt) { m_Lock.Lock(Exclusive); };
            ~TAutoLockEx() { m_Lock.Unlock(Exclusive); }

            private:
            LockType& m_Lock;
        };
    }
}